The invention is related to a floating-caliper spot-type disc brake which is particularly designed for high performance.
Automotive vehicles which reach high driving speeds need high performance brakes, which require as large as possible a brake disc diameter, while the diameter of the vehicle wheels cannot be increased because of other considerations. The mounting space for the brake is thus severely restricted between the external edge of the brake disc and the predetermined diameter of the wheel rim. The brake caliper of a disc brake customarily straddles the external edge of the brake disc, with a bridge of the brake caliper positioned in the forementioned mounting space, and thus the radial dimension of the bridge limits the maximum diameter of the brake disc. The caliper bridge must, on the other hand, have a determined minimum thickness because it transmits the clamping forces which are required for braking action.
From the European patent specification, No. 0 412 541 a disc brake suitable for a high brake power is known, having a brake caliper in the shape of a floating frame which is axially slidingly guided on a brake carrier. The brake carrier in turn is mounted to the steering knuckle of the vehicle by means of pin guides which extend axially beyond the external edge of the brake disc. The floating frame encloses four brake shoes which are disposed on either side of the brake disc and transmits the clamping force. The circumferential forces are transmitted by the brake shoes to the brake carrier. The brake carrier is coupled to the vehicle on the axially internal side of the wheel. In order to be able to also absorb the circumferential forces of the two axially external brake shoes, the brake carrier is furnished with a carrier arm which straddles the external edge of the brake disc.
High-performance brakes require large brake shoe friction surfaces. However an increase in size of the brake shoes particularly in the circumferential direction of the brake disc has the disadvantage that the friction surface is no longer uniformly pressed against the brake disc, even if two brake cylinders arranged side by side are used.
Beyond this, large brake shoes tend to generate braking noises and rubbing, especially when the circumferential force which occurs during braking is transmitted by the brake shoe to the brake housing on the exit side of the brake disc. For this reason, two short-size brake shoes are used which are pressed against the brake disc separately from each other by two brake pistons which are arranged one beside the other.
Another requirement of a high-performance brake is that its weight must be as low as possible. Indeed, heavy brakes present a particular problem because this increases the unsprung masses at the vehicle wheels. This, in turn, has negative effects on the driving performance of the vehicle. The brake power cannot for this reason be increased simply by increasing the brake size.
It is the object of the invention to create a floating-caliper spot-type disc brake with high brake power which does not generate excessive noise and rubbing.